Seventeen adult males and females with Hb-SS, Hb-SC (1) and Hb-S Thal (1) hemoglobinopathies were continuously studied for 3 years. Various hematological and biochemical parameters were measured in the venous blood of the subjects for blood gases, CBC profile, blood chemistry (SMA-18), fibrinogen, alpha-HBD and myoglobin levels, percent sickling, blood viscosity, oxygen affinity of whole blood, osmofragility of red blood cells and calcium and zinc contents in plasma and in RBC. The results were compared between those subjects who encountered more frequent vaso-occlusive crisis episodes (frequent sicklers) and those with fewer crisis episodes (infrequent sicklers), along with parameters between crisis and non-crisis states of frequent sicklers. Our studies showed that percent sickling, P50 for O2, CBC profile, PO2, serum calcium, ALP, LDH, alpha-HBD level, zinc and calcium levels in plasma and in RBC varied between crisis and non-crisis states of frequent sicklers and also between frequent sicklers and infrequent sicklers. A logical explanation of such variations may help in understanding the etiology of vaso-occlusive crisis episodes in sickle cell disease.